全文获取类型
收费全文 | 25080篇 |
免费 | 1850篇 |
国内免费 | 77篇 |
专业分类
耳鼻咽喉 | 378篇 |
儿科学 | 675篇 |
妇产科学 | 534篇 |
基础医学 | 3119篇 |
口腔科学 | 278篇 |
临床医学 | 2561篇 |
内科学 | 5391篇 |
皮肤病学 | 486篇 |
神经病学 | 2301篇 |
特种医学 | 1197篇 |
外科学 | 4082篇 |
综合类 | 255篇 |
一般理论 | 23篇 |
预防医学 | 1822篇 |
眼科学 | 408篇 |
药学 | 1766篇 |
中国医学 | 28篇 |
肿瘤学 | 1703篇 |
出版年
2023年 | 292篇 |
2022年 | 559篇 |
2021年 | 1140篇 |
2020年 | 629篇 |
2019年 | 950篇 |
2018年 | 1053篇 |
2017年 | 712篇 |
2016年 | 741篇 |
2015年 | 928篇 |
2014年 | 1183篇 |
2013年 | 1470篇 |
2012年 | 2135篇 |
2011年 | 2165篇 |
2010年 | 1151篇 |
2009年 | 923篇 |
2008年 | 1427篇 |
2007年 | 1431篇 |
2006年 | 1355篇 |
2005年 | 1174篇 |
2004年 | 1041篇 |
2003年 | 887篇 |
2002年 | 790篇 |
2001年 | 245篇 |
2000年 | 160篇 |
1999年 | 194篇 |
1998年 | 146篇 |
1997年 | 110篇 |
1996年 | 110篇 |
1995年 | 79篇 |
1994年 | 63篇 |
1993年 | 60篇 |
1992年 | 118篇 |
1991年 | 101篇 |
1990年 | 91篇 |
1989年 | 102篇 |
1988年 | 73篇 |
1987年 | 88篇 |
1986年 | 75篇 |
1985年 | 74篇 |
1984年 | 66篇 |
1983年 | 54篇 |
1982年 | 56篇 |
1981年 | 60篇 |
1980年 | 43篇 |
1979年 | 52篇 |
1978年 | 45篇 |
1974年 | 37篇 |
1973年 | 48篇 |
1972年 | 47篇 |
1970年 | 40篇 |
排序方式: 共有10000条查询结果,搜索用时 0 毫秒
61.
Miscarriage rates following in-vitro fertilization are increased in women with polycystic ovaries and reduced by pituitary desensitization with buserelin 总被引:3,自引:10,他引:3
Balen Adam H.; Tan Seang-Lin; MacDougall Jane; Jacobs Howard S. 《Human reproduction (Oxford, England)》1993,8(6):959-964
To assess the risk of miscarriage after in-vitro fertilization(IVF) with respect to age, cause of infertility, ovarian morphologyand treatment regimen, a retrospective analysis was performedof the first 1060 pregnancies conceived between June 1984 andJuly 1990 as a result of 7623 IVF cycles. Superovulation inductionwas achieved with human menopausal gonadotrophin (HMG) and/orpurified follicle stimulating hormone (FSH) together with eitherclomiphene citrate or the gonadotrophin hormone-releasing hormone(GnRH) agonist buserelin, the latter either as a short flareregimen or as a long regimen to induce pituitarydesensitization. There were 282 spontaneous abortions (26.6%)and 54 ectopic pregnancies (5.1%). The mean age of women withongoing pregnancies was 32.2 (SD 3.9) years compared with 33.2(SD 4.1) years in those who miscarried, which were significantlydifferent (P = 0.008). There was no relation between the miscarriagerate and the indication for IVF. The miscarriage rate was 23.6%in women with normal ovaries compared with 35.8% in those withpolycystic ovaries [P = 0.0038, 95% confidence interval (CI)4.6823.10%]. There was no difference in the miscarriagerate between treatment with HMG or FSH. Women whose ovarieswere normal on ultrasound were just as likely to miscarry ifthey were treated with clomiphene or with the long buserelinprotocol. Those with polycystic ovaries, however, had a significantreduction in the rate of miscarriage when treated with the longbuserelin protocol, 20.3% (15/74), compared with clomiphenecitrate, 47.2% (51/108) (P = 0.0003, 95% CI 13.8240.09%). 相似文献
62.
Kim W Koo H Richman AM Seeley D Vizioli J Klocko AD O'Brochta DA 《Journal of medical entomology》2004,41(3):447-455
Genetically altering the disease vector status of insects using recombinant DNA technologies is being considered as an alternative to eradication efforts. Manipulating the endogenous immune response of mosquitoes such as the temporal and special expression of antimicrobial peptides like cecropin may result in a refractory phenotype. Using transgenic technology a unique pattern of expression of cecropin A (cecA) in Anopheles gambiae was created such that cecA was expressed beginning 24 h after a blood meal in the posterior midgut. Two independent lines of transgenic An. gambiae were created using a piggyBac gene vector containing the An. gambiae cecA cDNA under the regulatory control of the Aedes aegypti carboxypeptidase promoter. Infection with Plasmodium berghei resulted in a 60% reduction in the number of oocysts in transgenic mosquitoes compared with nontransgenic mosquitoes. Manipulating the innate immune system of mosquitoes can negatively affect their capacity to serve as hosts for the development of disease-causing microbes. 相似文献
63.
Lyashchenko K Whelan AO Greenwald R Pollock JM Andersen P Hewinson RG Vordermeier HM 《Infection and immunity》2004,72(5):2462-2467
Vaccine development and our understanding of the pathology of bovine tuberculosis in cattle would be greatly facilitated by definition of the immunological correlates of protection and/or pathology. In this study we analyzed humoral immune responses in Mycobacterium bovis BCG-vaccinated and control cattle (in particular, the relationship between the intradermal comparative tuberculin skin test and serum immunoglobulin G [IgG] responses) against a range of mycobacterial antigens (MPB59, MPB64, MPB70, MPB83, ESAT-6, CFP-10, Acr1, and PstS-1) by multiantigen print immunoassay and conventional enzyme-linked immunosorbent assay. Following M. bovis infection, the comparative tuberculin skin test strongly boosted IgG, IgG1, and IgG2 antibody responses, particularly against MPB83 and MPB70, in unvaccinated cattle but failed to boost these responses, or did so only weakly, in BCG-vaccinated calves. In addition, the skin test-induced increases in MPB83-specific IgG responses correlated positively with bacterial loads and ESAT-6-induced in vitro gamma interferon responses. In conclusion, both the negative correlation of skin test-enhanced MPB83-specific antibody responses with BCG-induced protection and their positive correlation with bacterial loads can serve as useful markers for vaccine efficacy after challenge. 相似文献
64.
Terminal bronchioles harbor a unique airway stem cell population that localizes to the bronchoalveolar duct junction 总被引:14,自引:0,他引:14 下载免费PDF全文
Cellular mechanisms contributing to renewal of terminal bronchioles remain poorly defined. Our previous studies identified pollutant-resistant Clara cell secretory protein (CCSP)-expressing stem cells that localize to the neuroepithelial body (NEB) and contribute to renewal of the proximal bronchiolar epithelium. However, activation of NEB-associated stem cells is unlikely to contribute to renewal of terminal bronchiolar epithelium because of the paucity of NEBs at this location. Goals of this study were to determine the location and properties of cells contributing to renewal of terminal bronchioles after Clara cell depletion. Pollutant-resistant CCSP-expressing cells were identified that localized to the bronchoalveolar duct junction (BADJ) and contribute to restoration of a phenotypically diverse epithelium. CCSP-expressing cells comprise the predominant proliferative population in initial terminal bronchiolar repair and include a population of label-retaining cells suggesting that they maintain characteristics of a stem cell population. Furthermore, immunohistochemical co-localization studies involving CCSP and the NEB-specific marker calcitonin gene-related peptide indicate that BADJ-associated CCSP-expressing stem cells function independently of NEB microenvironments. These studies identify a BADJ-associated, NEB-independent, CCSP-expressing stem cell population in terminal bronchioles and support the notion that regiospecific stem cell niches function to maintain epithelial diversity after injury. 相似文献
65.
In vitro degradation of silk fibroin 总被引:14,自引:0,他引:14
Horan RL Antle K Collette AL Wang Y Huang J Moreau JE Volloch V Kaplan DL Altman GH 《Biomaterials》2005,26(17):3385-3393
A significant need exists for long-term degradable biomaterials which can slowly and predictably transfer a load-bearing burden to developing biological tissue. In this study Bombyx mori silk fibroin yarns were incubated in 1mg/ml Protease XIV at 37 degrees C to create an in vitro model system of proteolytic degradation. Samples were harvested at designated time points up to 12 weeks and (1) prepared for scanning electron microscopy (SEM), (2) lyophilized and weighed, (3) mechanical properties determined using a servohydraulic Instron 8511, (4) dissolved and run on a SDS-PAGE gel, and (5) characterized with Fourier transform infrared spectroscopy. Control samples were incubated in phosphate-buffered saline. Fibroin was shown to proteolytically degrade with predictable rates of change in fibroin diameter, failure strength, cycles to failure, and mass. SEM indicated increasing fragmentation of individual fibroin filaments from protease-digested samples with time of exposure to the enzyme; particulate debris was present within 7 days of incubation. Gel electrophoresis indicated a decreasing amount of the silk 25 kDa light chain and a shift in the molecular weight of the heavy chain with increasing incubation time in protease. Results support that silk is a mechanically robust biomaterial with predictable long-term degradation characteristics. 相似文献
66.
Paul K. Hildebrandt James D. Conroy Adam E. McKee M. B. A. Nyindo David L. Huxsoll 《Infection and immunity》1973,7(2):265-271
The ultrastructure of Ehrlichia canis was examined in both pulmonary mononuclear cells and in monocytes cultured from an infected dog. The cytoplasmic inclusions, or morulae, of E. canis consisted of a membrane-lined vacuole-containing elementary bodies which varied in size and number. The elementary bodies were bound by two trilamellar membranes. The organism shared morphological properties of both the genus Rickettsia and genus Chlamydia. 相似文献
67.
The complete sequence of the coding region of the ATM gene reveals similarity to cell cycle regulators in different species 总被引:30,自引:3,他引:30
Savitsky Kinneret; Sfez Sharon; Tagle Danilo A.; Ziv Yael; Sartiel Adam; Collins Francis S.; Shiloh Yosef; Rotman Gallt 《Human molecular genetics》1995,4(11):2025-2032
Ataxia-telangiectasia (A-T) is an autosomal recessive disorderinvolving cerebellar degeneration, immunodeficiency, radiationsensitivity, and cancer predisposition. A-T heterozygotes aremoderately cancer prone. The A-T gene, designated ATM, was recentlyidentified in our laboratory by positional cloning, and a partialcDNA clone was found to encode a polypeptide with a PI-3 kinasedomain. We report here the molecular cloning of a cDNA contigspanning the complete open reading frame of the ATM gene. Thepredicted protein of 3056 amino acids shows significant sequencesimilarities to several large proteins in yeast, Drosophilaand mammals, all of which share the PI-3 kinase domain. Manyof these proteins are involved in the detection of DNA damageand the control of cell cycle progression. Mutations in theirgenes confer a variety of phenotypes with features similar tothose observed in human A-T cells. The complete sequence ofthe ATM gene product provides useful clues to the function ofthis protein, and furthers understanding of the pleiotropicnature of the A-T mutations. 相似文献
68.
H. Seibold E. Henze J. Kohler J. Roth A. Schmidt W. Adam 《Journal of molecular medicine (Berlin, Germany)》1985,63(20):1041-1047
Summary Simultaneous right heart catheterization and radionuclide ventriculography were performed in 27 patients with a wide range of chronic obstructive pulmonary disease. Central hemodynamics and radionuclide studies were done at rest and during exercise. In the resting state the right ventricular ejection fraction (RVEF) was in the normal range (43.3±6%). During exercise a significant (p<0.001) decrease of RVEF to 38.8±6.7% occurred. The pumonary artery mean pressures were 19.9±3.8 at rest. During exercise a significant (p<0.001) increase to 41±9.8 mm Hg occurred. There was a linear relationship between pulmonary pressures and RVEF during exercise in patients with pulmonary artery pressures not exceeding 35 mm Hg. In patients with right ventricular end-diastolic wall thickness 6 mm a curvilinear relationship between these parameters could be observed with a flattening of the curve at higher pressures (>35 mm Hg) and lower ejection fractions (<35% RVEF). Radionuclide venticulography cannot substitute for right heart catheterization. Echocardiography is useful for interpretation of right ventricular ejection fractions in advanced chronic obstructive pulmonary disease.Abbreviations CI
Cardiac index (l/min/m2)
- CO
Cardiac output (l/min)
- COPD
Chronic obstructive pulmonary disease
- FEV1
Forced expiratory volume in the first second (ml)
- HR
Heart rate (B/min)
- PAd
Pulmonary artery diastolic pressure (mm Hg)
- PAP
Pulmonary artery mean pressure (mm Hg)
- PAs
Pulmonary artery peak pressure (mm Hg)
- PVR
Pulmonary vascular resistance (dyn·s·cm–5)
- PwP
Pulmonary capillary wedge pressure (mm Hg)
- RAP
Right arterial pressure (mm Hg)
- Raw
Airway resistance (cm H2/l/s)
- RNV
Radionuclide ventriculogram
- RV
Residual volume (l)
- RVEF
Right ventricular ejection fraction (%)
- RVEDVI
Right ventricular enddiastolic volume index (ml/m2)
- RVEDVI
SVI RVEF (ml/m2)
- RVESVI
Right ventricular endsystolic index (m2/m2)
- SVI
Stroke volume index (ml/m2)
- TLC
Total lung capacity (l)
- VC
Vital capacity (l) 相似文献
69.
Pelisek J Engelmann MG Golda A Fuchs A Armeanu S Shimizu M Mekkaoui C Rolland PH Nikol S 《Journal of molecular medicine (Berlin, Germany)》2002,80(11):724-736
Cationic liposomes/DNA complexes are widely used vectors for delivering genes in clinical and experimental trials. Relatively low transfer efficiencies in vivo compared with viral gene transfer may be improved using local application. In addition, markedly increased transfer efficiency may be achieved in vitro and in vivo via optimization of known variables influencing liposomal transfection. Lipofection under different conditions was performed in various cell lines and primary porcine smooth muscle cells. Optimized conditions found in vitro were verified in vivo using a porcine restenosis model. Toxicity was monitored analyzing cell metabolism. Transfer efficiency and safety were determined using morphometry, histology, galactosidase assays, PCR, and RT-PCR. The most important variables enabling maximum transfer efficiency were firstly the appropriate selection of cationic lipids for the cell type to be transfected, secondly the DNA/liposome ratio chosen, which depended on the cell type and cationic lipids used, and thirdly the state of proliferation of the targeted cells. Transfection in vivo demonstrated two- to fivefold higher transfer efficiencies when transfer conditions were extrapolated from optimization experiments in stationary cells compared with the use of conditions established in proliferating cells. Application of the therapeutic gene for cecropin using optimized transfer conditions resulted in a significantly reduced neointima formation compared with the transfection using a control gene for ss-galactosidase. Thus, in this vascular model, initial optimization of lipofection in stationary cells in culture followed by local delivery in vivo and with selection of a suitable therapeutic gene led to markedly improved transfer efficiencies, gene expression, and biological effect. Stationary cell cultures simulate more realistically the in vivo situation and may therefore represent a better model for future in vivo experiments. In addition, the advantages of liposomes are easy handling, low toxicity, and the lack of carcinogenicity or immunogenic reactions. 相似文献
70.